1. Field of the Invention
The present invention relates to a backlight unit, and more particularly, to a backlight unit in an electrode PCB structure, capable of determining a deviated degree of a lamp grip by a guide line formed adjacent to the lamp grip on the PCB that connects an electrode thereof with a lamp electrode, and a manufacturing method for the same.
2. Discussion of the Related Art
A cathode ray tube (CRT), one type of generally utilized displaying devices, is applied mainly to monitors of TVs, measuring equipments, information terminals and the like. Recently, however, because the CRT has such great weight and size, it has been going out of date due to the tendency toward compact and lightweight electronic products.
Since the ability to reduce the size and weight of a CRT is limited, various technologies for replacing the CRT have been developed, including a liquid crystal display (LCD) using the electric-field effect and the optical effect, a plasma display panel (PDP) using a gas discharge, an electro-luminescence display (ELD) using the electro-luminescence effect and the like. The LCD among the above devices is being actively researched.
Because it is compact, lightweight, and economical in power consumption, the LCD is being actively researched and developed as a substitute for the CRT. Accordingly, now being competent to serve as a flat panel display, the LCD is applied to monitors of a desk-top computer as well as a laptop computer, and huge-size information displays. Thus, the demand for the LCD is continuously increasing.
Most of the LCDs are light receiving types that display an image by adjusting luminosity of an incident light from the outside. Therefore, in order to project light to an LCD panel, the LCD is necessarily equipped with a dedicated light source such as a backlight unit.
In general, the backlight unit used as a light source of the LCD is divided largely into an edge type and a direct type, in accordance with the arrangement of cylindrical light emitting lamps.
In the edge-type backlight unit, a lamp unit is mounted to a side edge of a light guide plate that guide light. More particularly, the lamp unit comprises a light emitting lamp, a lamp holder inserted in both ends of the lamp to protect the lamp, and a lamp reflection plate enclosing an outer circumference of the lamp, being inserted in a lateral side of the light guide plate by one side thereof so as to reflect the light emitted from the lamp toward the light guide plate.
Usually, the above-structured edge-type backlight unit wherein the lamp unit is formed at the side edge of the light guide plate is applied to relatively small LCDs such as monitors of a laptop computer and a desktop computer. The edge-type backlight unit has excellent uniformity of light and durability, and is advantageous to implement such thin LCDs.
On the other hand, the development of direct-type backlight unit has been concentrated since the appearance of a large LCD over 20 inches. The direct-type backlight unit is structured in a manner that a plurality of lamps are linearly arranged on a lower surface of a diffusion plate to directly illuminate the whole surface of the LCD panel.
Having a higher light use efficiency than the edge type, the direct type is mainly used in a large-size LCD which requires high brightness.
In addition, the direct type can apply a variety of methods for applying voltage signals for driving the respective lamps.
Hereinafter, a backlight unit according to the conventional art will be described with reference to the accompanying drawing.
FIG. 1 is a plan view of the conventional backlight unit.
Referring to FIG. 1, the backlight unit comprises a case structure 1 and a plurality of lamps 2 arranged in the case structure 1 at constant parallel intervals. A voltage applying line 4 is provided to both ends of each lamp 2 and connected to a lamp driving unit 5 mounted at the outside. In this case, electrodes disposed at both ends of the lamp 2 are connected with the voltage applying lines 4 by soldering. However, since at least twice as many voltage applying lines 4 as the number of the lamps 2 are necessary, soldering may be insufficient to perfectly connect the lamp electrodes with the voltage applying lines 4 without a short circuit. Therefore, the structure needs to be improved. In this example, a rubber holder 3 is applied to the both electrodes of the lamp 2.
Recently, it has been suggested that the lamp electrodes and driving signal applying parts are in the form of an electrode PCB and corresponded to the plurality of lamp electrodes in order to minimize the soldering process and the voltage applying lines.
The above conventional direct-type backlight unit have some problems as follows.
Since at least twice as many voltage applying lines as the number of the lamps are required, the soldering connection may cause a short circuit. Therefore, the structural improvement is necessitated.
To reduce the soldering process and minimize the number of the voltage applying lines, the electrodes of the lamps and the driving signal applying part have been changed to the electrode PCB form to be are corresponded to the plurality of lamp electrodes. However, because the electrode PCB is separately manufactured from the lamp, the shape of a connection part with the lamp is hard to correctly correspond to the lamp and even subject to distortion. Furthermore, when the connection part of the electrode PCB, as partially distorted, is connected with the lamp, the lamp may be continuously applied with an external force and therefore even deformed or broken. To this end, it is required to minimize distortion between the lamp and the connection part of the PCB electrode.